1. Field of the Invention
The present invention relates to roller coaster wheels.
2. Description of the Prior Art
Roller coasters have for centuries been a popular form of entertainment and distraction in nearly every developed country, starting in about the 17th century with the ice slides in Russia involving the frame work constructed of the lumber with several inches of thick ice covering the surface so that sliders could speed down the 50° drop. By the mid to late 1700's wheels had been added to roller coaster cars and as design improvements continued, methods where devised for locking the cars unto the tracks and for guiding the cars along the tracks and the application of the brakes for slowing the speed of the car. After some slackening, wooden frame roller coasters have now regained their popularity, growing to over 3,000 feet in length and some 70°-75° and beyond in the first drop with undulations providing for fast to slow and back to fast several times throughout the course with twisting layouts and challenging contours providing for good, violent rides.
Many installations provide trains of cars including multiple wheels on each car which may involve 80 to 100 wheels per roller coaster train. The wheels are subjected to high stresses and strain throughout the maneuvers of the roller coaster trains while they experience changes in angular acceleration as they wind along their paths, through curves, variations in elevation and positive and negative G's, repetitively stressing the wheels and applying high loads thereto. The wheels may have an outside diameter on the order of 4 to 12 inches and the tread surfaces thereof are typically in direct contact with the tracks often making metal to metal contact and experiencing the abrasive effect of dirt or grit captured between the wheels and the tracks and the repetitive pounding of metal on metal which, in spite of shock absorbers sometimes incorporated in the vehicles, tends to shock the wheels and shorten their service lives. Efforts have been made to smooth out track installations in effort to reduce the loads and fatigue on the wheels but this is generally an imperfect construction and maintenance process. It is also been proposed to incorporate plastic tread in the form of urethanes and the like in effort to absorb the shock and extend the life of the wheels but, such treads typically wear relatively rapidly resulting in high maintenance expenses for replacement and repair.
Those working in the art have recognized that steel wheels, while providing structure and integrity, are extremely expensive and little flex or give which might absorb the high impact shock applied to the wheels. In other areas of wheel design, numerous different constructions have been proposed to provide hard, impact resistant tread surfaces. An early examples is wooden or cast wheel bodies having a circular periphery about which was formed a wear and shock resistant tread band. One of the challenges addressed has been the efficient and positive attachment of the band to the wheel in effort to resist shock, separation and wear and tear to provide for a long life. One such solution was to provide a strip of steel to be bent in a circle about the wheel body to bring the opposite ends into confronting spaced relationship exhibiting a small gap so that the band could be heated to provide thermal expansion and closure of the gap for welding or other attachment to hold the band closed so that, upon cooling it would provide a high friction grip to the wheel. A device of this type is shown in U.S. Pat. No. 1,947,462 to Doorbar.
Other multiple component designs have been proposed for model trains to provide for electrical insulation between the tracks and wheel bodies. A device of this type is shown in U.S. Pat. No. 2,558,384 to Pritchard.
In recognition of the short comings of roller coaster wheels with urethane treads which require frequent replacement and maintenance, a split wheel construction has been proposed for sandwiching a rim therebetween for mounting a urethane tire to thereby reduce the labor intensive process of repairing the wheels. A device of this type is shown in U.S. Patent Application No. 2003/0205909 to Bradley.
Large diameter railroad wheels are typically constructed of steel and are relatively expensive to replace. Thus, it has been proposed to, when a railroad wheel become warn or out of round, to machine the exterior surface thereof and, to anodize the surface and apply the steel ring to the machined wheel to thus simulate the flanged exterior diameter of a new wheel. A device of this type is shown in U.S. Patent Application No. 2009/0218837 to Mantkowski.
Aluminum roller coaster wheels have been proposed for both the weight bearing function as well as guiding of roller coaster itself. It has been recognized that, particularly with respect to the guide wheels, the wheels are disengaged from contact with the guide rail and may thus slow down in their rotation or come into a complete stop such that when the fast moving roller coaster carries the non-rotating wheel into contact with a guide rail, high angular acceleration is experienced as well skidding engagement with the rail thus severely limiting the life of the wheel. In effort to reduce the attendant shock and noise it has been proposed to provide the wheels with a tread of plastic. A wheel of this type is shown in U.S. Pat. No. 6,093,266 to Mollee.
Steel wheels remain popular today. It is believed that these steel wheels, because of their geometry and material characteristics, are very effective emitters of high frequency sound and are the source of severe squeal noise, a noise associated with a complex combination of creepage between the wheel and ash track and a mechanism known in the art as “stick-slip”. Stick-slip occurs when the process of creepage overcomes the ability of a wheel-rail at the interface to impart rotation at the speed of travel and the wheel ends up sliding relative to the rail or track. The friction between the wheel and rail tends to resist stick-slip but, when the friction is overcome and the lateral movement of the wheel relative on the flat top surface of the rail occurs, energy is released as a high pitched noise and the process then starts over again. This rapidly oscillating wheel-rail contact force can excite vibration of the central portion of the wheel which then radiates a high pitch squeal. This, plus the mass of a steel wheel which imparts high forces with high angular acceleration tends to limit service life, pose a danger from breakage and contribute to noise pollution.